1. Field of the Invention
The present invention is directed to an apparatus for and a method of folding a mast or derrick. In particular, the present invention is directed to a folding mast or derrick that may be efficiently assembled and then disassembled and readily transported from one well site to another.
2. Related Art
Well drilling rigs in oil and gas operations are utilized to drill for reserves. Many times drilling does not result in a productive well and it has been estimated that over two million bore holes have been dug worldwide.
Masts or derricks are well known for use in oil and gas and other drilling operations. The mast or derrick may be mounted on a fixed platform or on a jackup platform above ground level over a well bore. A mast often extends up to two hundred feet above a drill floor and is often composed of structural steel framework which supports a crown assembly. A mast or derrick of a drilling rig supports a vertically moving block and tackle in order to raise and lower a series of drill pipes which support a drill bit.
One type of known portable derrick structure is disclosed in Kennard, Jr. (U.S. Pat. No. 4,651,884) which is mounted on a vehicle. The derrick is movable between horizontal and vertical positions.
One well known type of drilling structure includes a pair of sides with a back face joining the sides and an open front or V-door face. A mast is, accordingly, typically braced or cross braced on three sides with an open front face to receive and remove pipe sections and other equipment.
The mast or derrick itself may be composed of a lower or bottom mast section assembly connected to a drill floor and one or more upper mast section assemblies connected thereto on top of the lower mast section. In some configurations, the lower or bottom mast section is wider than the other mast sections.
As drilling is conducted, the drill bit becomes dull or broken and the whole drill string has to be taken out of the hole and the bit repaired or replaced. In addition, in some applications, casing, consisting of thick-walled pipes, are screwed together and lowered into the well.
From time to time, once a drilling project has been completed, it is required to move the drilling rig from one location to another location. In one known process, the entire drilling rig is disassembled piece by piece, then transported to the next location, and then reassembled piece by piece. This process is both labor intensive and time consuming.
As a technological advance on the complete disassembly and reassembly of the mast or derrick, a folding gin pole or A-pole arrangement was developed. The entire mast could be moved from vertical to horizontal position by a wire line extending from the crown assembly to a gin pole or A-pole at the base of the rig. Once in the horizontal position on the ground, the mast could thereafter be disassembled.
In many applications, the mast sections are transported by trailer. Disassembly of the mast sections is normally required due to roadway limits such as height and width.
It would be desirable to fit the various masts sections on to trailers for highway transportation with a minimum of disassembly.
Additionally, it would be advantageous for the mast sections to be able to meet roadway requirements for size of load. For example, certain highway regulations limit the width of the load to 12 or 14 feet. Accordingly, it would be advantageous to provide a mast or derrick wherein the mast sections may be reduced in size for transportation to a width acceptable for roadway requirements.
It would also be advantageous to provide a mast or derrick having sections that may be moved between an open, in-use position and a folded position for storage and transportation.
It would also be advantageous to provide a mast or derrick having sections that may be locked in either an open, in-use position or a folded position for storage and transportation.
It would also be advantageous to provide a mast or derrick that may be moved between an open in-use position and a folded position utilizing hydraulic cylinders.
It would also be advantageous to provide a mast or derrick wherein the required disassembly and subsequent re-assembly is reduced.
It would also be advantageous to provide a method of folding a mast wherein the block and tackle may be secured to a mast section during transportation and accordingly, disassembly is not required.
Assignee's prior patent (Brittain et al. U.S. Pat. No. 6,594,960) shows an example of articulating a back face of a mast or derrick using a crane and a forklift.
It would also be advantageous to provide a method of moving a mast or derrick between an open, in-use position and a folded position utilizing existing hydraulic systems on the drilling rig at the well site.